I believe that you mean "portocaval shunt." This is a surgical procedure in which the portal vein which normally provides blood flow to the liver is attached to the vena cava. This is performed in people who have portal hypertension which is frequently related to liver cirrhosis. The shunt decompresses the hypertension to decrease the risk of bleeding from varices. Unfortunately, you also bypass the liver so that certain toxins are not cleared as efficiently from the body so the patient can experience changes in their mental status.